LiPbSb3S6: A Semiconducting Sulfosalt with Very Low Thermal Conductivity

The new semiconductor LiPbSb3S6 crystallizes in the space group P21/c. The structure is a member of the lillianite homologous series and is composed of layers of PbS archetype Sb/Li–S separated by trigonal-prismatic-coordinated Pb/Li. Electronic band structure calculations indicate an indirect band gap, with direct gaps lying very close in energy. LiPbSb3S6 has one of the lowest thermal conductivities seen in a crystalline material, ∼0.24 W m–1 K–1 at room temperature, and a high resistivity, ∼4 × 109 Ω·cm, and exhibits strong light absorption with a nearly direct band gap of 1.6 eV.